Measuring intramucosal pH in very low birth weight infants

Measurement of gastric-to-end-tidal carbon dioxide difference in neonates requiring intensive care

OBJECTIVE

Gastric-arterial partial CO(2) pressure gap (P(g-)(a)CO(2) gap) measured by gastric tonometry may detect the disturbance of splanchnic perfusion. As in the neonatal age it is very difficult to follow up the circulatory condition with frequent acid-base examinations, we wanted to compare the P(g-)(a)CO(2) gap with an alternative gap of P(g)CO(2) - end-tidal carbon dioxide (P(g)(-)(ET)CO(2) gap).

METHODS

A prospective study was performed on ventilated neonates requiring intensive therapy (n = 44, weight: 1813 ± 977 g). P(ET)CO(2) and P(g)CO(2) were measured with a side stream capnograph. We applied a newly developed gastric tonometric probe. Patients were divided into two groups: Group 1 of patients in stable condition (n = 35) and Group 2 of patients with severe condition (i.e. Clinical Risk Index for Babies [CRIB] score higher than 10; n = 9). For main statistical analysis a mixed model repeated measurements ANOVA, Bland-Altman analysis were applied.

RESULTS

P(g)(-)(ET)CO(2) gap was higher than P(g-)(a)CO(2) gap (11.40 ± 7.79 versus 3.63 ± 7.98 mmHg, p < 0.01). Both gaps were higher in Group 2 (8.71 ± 10.89 and 18.27 ± 10.49 versus 2.53 ± 6.78 and 9.92 ± 6.22 mmHg, p < 0.01 and p < 0.05). Bland-Altman analysis of the two gaps showed an acceptable correspondence.

CONCLUSIONS

P(g)(-)(ET)CO(2) gap may be used as a method for continuous estimation of splanchnic perfusion and a prognostic index also in critically ill neonates. However, the P(g-)(a)CO(2) gap should not be abandoned.

Physiological impact of pneumoperitoneum on gastric mucosal CO2 pressure during laparoscopic versus open appendectomy in children

INTRODUCTION

Funded knowledge about the physiological impact of laparoscopic surgery in children is sparse. Although there are data on hemodynamic compromise after creation of a pneumoperitoneum in children, little is known about microcirculatory changes at the mucosa level. Therefore, the aim of this study was to assess gastric microcirculation by continuous gastric air tonometry in the setting of laparoscopic versus open appendectomy.

PATIENTS AND METHODS

Twenty children 5-17 years old undergoing laparoscopic and 7 children undergoing open appendectomy were included in the study. Gastric intramucosal CO(2) pressure (pCO(2)i) was measured under standardized flow and intraperitoneal pressure using continuous air tonometry (TONOCAP(®), Datex Ohmeda), and ΔpCO(2) (pCO(2)i - end-expiratory CO(2) pressure [pCO(2)e]) was obtained for the time course of surgery.

RESULTS

ΔpCO(2) increased significantly from the baseline value not only in the laparoscopic group but also in the open surgery group. Even though ΔpCO(2) was higher in the laparoscopic group at all time points, the overall increase in ΔpCO(2) for both groups was uniform. The largest differences were observed during the initial 20 minutes of the operation. The changes observed were exclusively due to an increase of pCO(2)i in relation to a constant pCO(2)e.

DISCUSSION

In the setting of a standardized, simple operation in an otherwise healthy child above the age of 5 years, our data suggest that the effect of a pneumoperitoneum on splanchnic perfusion is comparable to the compromise caused by open surgery. Further research must be obtained when evaluating the full impact of laparoscopy in children.

Evaluation and treatment of hypotension in the preterm infant

A large proportion of very preterm infants receive treatment for hypotension. The definition of hypotension is unclear, and, currently, there is no evidence that treating it improves outcomes or, indeed, which treatment to choose among the available alternatives. Assessment of circulatory adequacy of the preterm infant requires a careful clinical assessment and may also require ancillary investigations. The most commonly used interventions, fluid boluses and dopamine, are problematic: fluid boluses are statistically associated with worse clinical outcomes and may not even increase blood pressure, whereas dopamine increases blood pressure mostly by causing vasoconstriction and may decrease perfusion. For neither intervention is there any reliable data showing clinical benefit. Prospective trials of intervention for hypotension and circulatory compromise are urgently required.

The pediatric multiple organ dysfunction syndrome

OBJECTIVES

To review the epidemiology of pediatric multiple organ dysfunction syndrome (MODS) and summarize current concepts regarding the pathophysiology of shock, organ dysfunction, and nosocomial infections in this population.

DATA SOURCE

A MEDLINE-based literature search using the keywords MODS and child, without any restriction to the idiom.

MAIN RESULTS

Critically ill children may frequently develop multisystemic manifestations during the course of severe infections, multiple trauma, surgery for congenital heart defects, or transplantations. Descriptive scores to estimate the severity of pediatric MODS have been validated. Young age and chronic health conditions have also been recognized as important contributors to the development of MODS. Unbalanced inflammatory processes and activation of coagulation may lead to the development of capillary leak and acute respiratory distress syndrome. Neuroendocrine and metabolic responses may result in insufficient adaptive immune response and the development of nosocomial infections, which may further threaten host homeostasis.

CONCLUSIONS

Over the last 20 yrs, there has been an increasing knowledge on the epidemiology of pediatric MODS and on the physiologic mechanisms involved in the genesis of organ dysfunction. Nevertheless, further studies are needed to more clearly evaluate what is the long-term outcome of pediatric MODS.

Intraoperative gastric tonometric examinations in children and infants with a new probe, combined with measurement of the endtidal PCO2

BACKGROUND

Important progress relating to the early prediction of postoperative complications was recently achieved through the combined use of endtidal PCO(2) (P(ET)CO(2)) and gastric tonometry. The aim of this article was to present results obtained with a new tonometric instrument, proving its feasibility and extending its use to the control of anesthetized infants and children.

METHODS

The new tonometric probe, which is balloon free, consists basically of silicone rubber tubing. The room air initially inside the tubes of the probe equilibrates with the PCO(2) of the body cavity throughout its full length. The PCO(2) content of the gastric cavity (P(g)CO(2)) and simultaneously P(ET)CO(2) were measured with a microcapnograph. A total of 108 measurements were performed intraoperatively on 25 infants and young children operated on at the Surgical Unit of the Department of Pediatrics. The patients were divided into elective surgery cases <2 years of age, group I; elective surgery cases >2 years of age, group II; and acute surgery cases, independently of age, group III. To examine the degree of agreement between the measurements, Pearson's correlation coefficients were determined and Bland-Altman analysis was performed. A mixed model repeated measurements anova was used to compare the differences between the groups.

RESULTS

P(ET)CO(2) and P(g)CO(2) for groups I and II were nearly identical, and statistically not significantly different (mean difference 0.10 mmHg and 0.85 mmHg, P = 0.96 and 0.45, respectively), whereas the corresponding data for group III differed significantly from those for groups I and II (P = 0.03 and 0.001, respectively). On Bland-Altman analysis, the bias value for groups proved to be statistically significantly different (P = 0.001).

CONCLUSIONS

The tested new probe worked very well in small children. The clinical implications of the large gaps found between P(ET)CO(2) and P(g)CO(2) values in acutely ill children and children undergoing elective operations must be investigated further.

Hypotension and shock in the preterm infant

Between 16% and 98% of extremely preterm infants receive treatment for hypotension in the first few days of life. This enormous variation has arisen because of a lack of reliable information to create an evidence base for intervention. This review article provides the unique characteristics of the neonatal cardiovascular system, and addresses the definitions of hypotension and shock in the preterm infant, the indications for treatment and appropriate therapies in individual cases. The treatment of shock and hypotension in the preterm infant may be the area of neonatology where there is the greatest 'intervention/data imbalance'; more babies receive more treatments with less supportive evidence than in virtually any other domain. Treatment of hypotension in infants with good perfusion is probably unnecessary and may be harmful, but the assessment of adequate perfusion remains problematic. Infants with inadequate oxygen delivery to the tissues may benefit from treatment, but which treatments are effective are unknown. It is essential that better evidence be available to create a rational basis for intervention.

Blood flow parameters of the superior mesenteric artery as an early predictor of intestinal dysmotility in preterm infants

BACKGROUND

Blood flow parameters in the superior mesenteric artery (SMA) change with vasoconstriction or vasodilatation of the intestinal vascular bed. In cases of severe growth retardation as a result of haemodynamic disturbances, the blood flow changes persist into postnatal life.

OBJECTIVE

To assess early changes of Doppler sonographic blood flow parameters in the SMA for prediction of later intestinal motility disturbances in preterm infants and tolerance of enteral feeding during the first week of life.

MATERIALS AND METHODS

Doppler sonographic blood flow parameters in the SMA were measured on the first day of life and the following 5 days in 478 neonates with a birth weight below 1,500 g. According to the Doppler results, the neonates were divided into two groups-those with pathological parameters and those with normal blood flow parameters. Correlations between blood flow parameters, the development of intestinal dysmotility and the tolerated amount of enteral feeding were calculated.

RESULTS

Pathological blood flow parameters were observed in 148 neonates (group 1) and normal blood flow parameters in 330 neonates (group 2). Intestinal motility disturbance occurred in 125 neonates (83%) of group 1 and 47 neonates (15%) of group 2. Neonates in group 2 tolerated significantly more feed by the fifth day of life than neonates in group 1. Postnatal adaptation did not differ between the two groups, although the majority of neonates with intestinal dysmotility were small for gestational age. The predictive value of blood flow parameters for prediction of intestinal motility revealed high sensitivity and specificity by the first postnatal day, 2 or 3 days before development of clinical signs of intestinal dysmotility. There was a strong negative correlation between pathological pulsatility index on day 1 and the quantity of tolerated enteral feeding on day 5.

CONCLUSIONS

Pathological blood flow parameters in the SMA can predict problems of intestinal motility and tolerance of enteral feeding. With the early detection of these problems a prompt start of adequate therapy to avoid complications is possible.

Hypotension in the very low birthweight infant: the old, the new, and the uncertain

Hypotension occurs in up to 20% of very low birthweight infants, usually in the first 48 hours after birth. Its importance lies in its possible causal link with brain injury. Its management is controversial.

Factors affecting performance of air tonometry using the TONOCAP

Saline tonometry has been replaced by automated air tonometry (TONOCAP). As with saline tonometry there are some pitfalls to consider. We investigated the influence of different filling handicaps to the tonometry catheter sampling balloon on measurement of regional PCO2 (PrCO2). In an in vitro set-up, PrCO2 was measured using the TONOCAP at intervals of 10 minutes from a 8F tonometry catheter sampling balloon placed in a container with constant PCO2 (PcCO2). Catheter alarms displayed by the TONOCAP device were noted. The following experiments were performed: A) control measurement without modifications; B) adding deadspace of 7 ml into the sampling line; C) placing the sampling balloon in a 3 ml syringe; D) cross-clamping of the sampling balloon. Each experiment was performed four times using two catheters on two TONOCAP devices. Differences between PcCO2 and PrCO2 were calculated as Pc-rCO2. Results are presented as mean +/- SD and were compared using ANOVA with Scheffe's correction. Pc-rCO2 in the control set-up (A) amounted to 0.16 +/- 0.22%. Increasing catheter deadspace (B) resulted in a higher Pc-rCO2 of 3.2 +/- 0.57% (P < 0.0001). Restriction of balloon expansion (C) caused an Pc-rCO2 gap of 1.17 +/- 0.36% (P < 0.0001). With filling restriction (D) the Pc-rCO2 gap increased to 3.87 +/- 0.29% (P < 0.0001). The catheter alarms provided were not able to indicate all catheter problems and initial alarms disappeared although the problems continued. We conclude that impaired catheter deadspace to balloon volume relation can negatively influence accuracy of PrCO2 measurement by the TONOCAP.